1. Field of the Invention
The present invention relates to a plunger for use in an oil well and more particularly to such a plunger which is adapted for deployment on the lowermost terminus of a tubing string in a "sucker rod"-type oil pumping assembly for reciprocation thereof within a tubular barrel.
2. Description of the Prior Art
The use of oil wells having reciprocating plunger mechanisms has long been known. Typically, such wells are constructed having an actuating assembly deployed upon the surface of the ground which is commonly constructed in the manner of a walking beam. An elongated tubular barrel extends downwardly into the ground and communicates through oil-bearing subsurface strata, and an elongated rod or tubing string is mounted by the walking beam for axial reciprocation thereof by the beam within the tubular barrel. A plunger assembly is typically borne by the string for reciprocation therewith to effect a lifting of oil from the lowermost reaches of the barrel toward the surface.
The oil sought to be pumped from the well is commonly found deposited in reservoir rock which often is of an unconsolidated nature, similar to beach sand. The rock, in an unconsolidated state, has a tendency to be carried in and flow with the formation fluids and to be elevated with such fluids by action of the plunger and tubing string assembly. Such particulate matter often accumulates between the plunger assembly and the tubular barrel, causing damage to the plunger as well as the barrel and often necessitating removal of the pump from the well to permit the servicing, repair or exchange of damaged parts.
In some regions, contamination of the well with sand and the like is extremely common, in some cases necessitating the removal of the well assembly for repair and replacement on as frequent as a daily basis. The consequence of such damage, together with the removal of the tubing string and plunger, are costly in terms of both time and money. With some well bores extending in a range of from about 3,000 to 7,000 feet and more below the surface, the removal and replacement of the plunger assembly is a time-consuming process. Economically, the consequences of break-downs of the assembly include increased labor costs, the cost of replacement parts, and the loss of oil which would otherwise have been pumped during the "downtime" period during which the well is not in operation.
Various attempts have been made in the art to provide plunger assemblies and pumps constructed to overcome the susceptibilities of plungers to contamination from sand and other fine particulate matter. However, most such assemblies have been deficient in one or more respects. Some are simply almost totally ineffective at preventing the interposition of particulate matter in the interface between the plunger exterior surface and the tubular barrel interior surface. Others are constructed in such a manner that, while performing more effectively than the majority of commonly employed plungers, they nevertheless, when damaged or deteriorated, must be replaced substantially as a unit, thereby negating an appreciable portion of the cost savings which might otherwise be realized by their use.
Therefore, it has long been known that it would be desirable to have an improved plunger of simple, yet effective, construction and which is operable to exclude both fine and coarse particulate matter from the space between the exterior surface thereof and the interior surface of a typical well barrel, and further which is characterized by the ease of replacement and inexpensiveness of its component elements.